The only thing I have been able to find about ultrasonic humidifiers is that they create a mist by passing the water over a diaphragm vibrating at an ultrasonic frequency.
OK, but why does passing water over a diaphragm vibrating at an ultrasonic frequency turn it into mist? I have a couple of these and it’s pretty cool to take the nozzle off and watch it fire up, that mist coming bubbling up the exhaust chute. But I don’t know what creates the mist, why it rises inside the humidifier, and then falls again when it leaves.